Dresden 2006 – scientific programme
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O: Oberflächenphysik
O 13: Solid-liquid interfaces
O 13.11: Talk
Monday, March 27, 2006, 17:30–17:45, WIL C207
Benzene diffusion measurements using neutron and helium spin-echo — •Peter Fouquet1, Holly Hedgeland2, Andrew P. Jardine2, Gil Alexandrowicz2, William Allison2, and John Ellis2 — 1Institut Laue-Langevin, BP 156, F-38042 Grenoble Cedex, France — 2Cavendish Laboratory, Madingley Road, Cambridge CB3 0HE, UK
The accurate description of surface-molecule interaction potentials is crucial for a correct description of molecule dynamics in systems with a large fraction of molecules close to a surface, such as zeolithes, mesoporous confinements and real catalysts. Here we present a new approach using two techniques that will allow to extract the surface contribution to the dynamics of molecules in confinements by measuring bulk diffusion (neutron spin-echo, NSE) and surface diffusion (helium spin-echo, HeSE) on the same system on identical length scales. NSE is an established technique for the analysis of dynamics in the ps to 100 ns time window at molecular length scales in bulk samples. Recently, surface sensitivity could be introduced by translating the NSE principle to helium atom scattering [1].
In a prototype experiment we could show the complementarity of NSE and HeSE by studying benzene diffusion on graphite(0001) surfaces. We characterized the specific response by the two techniques in respect of signal, diffusion mechanism and possible exitation of phonons. The measured diffusion mechanisms and constants agree well between the two techniques and also with recent MD calculations.
[1] A.P. Jardine et al., Science 304 (2004) 1790.